This invention relates to a polarized light separation device, a method of fabricating the device and a projection display apparatus that uses this polarized light separation device.
FIG. 26 is a perspective drawing of a conventional polarization beam splitter. This device comprises triangular prisms to which polarized light separation films and aluminum reflective films are vapor-deposited and then the prisms are pasted together. To wit, prisms 71, 72, 73 and 74 are polished prisms made of the material BK7, and these four prisms form a unit that is repeated to make up the entire device. A polarized light separation film 75 is formed by vapor deposition as inorganic thin films on that surface of the prism 72 which is facing the prism 71. In addition, an aluminum reflective film 76 is vapor-deposited on that surface of the prism 73 which is facing the prism 74. The prisms 71, 72, 73 and 74 are pasted to each other""s surfaces with adhesive. When a light beam 77 enters the prism 72, at the polarized light separation film 75, the P-polarized light component with respect to the plane of incident light passes through the prism 71 as transmitted light 77 and exits. On the other hand, the S-polarized light component is reflected by the polarized light separation film 75 then enters the prism 73, is reflected by the reflective film 76 and leaves the device as an S-polarized light beam 78. In this manner, a conventional polarization beam splitter is formed by pasting together prisms each of that has a polarized light separation film or a reflective film in a repetitive structure.
In the conventional method, the triangular prisms are each individually polished, vapor-deposited and pasted together, so it is not possible to reduce the size of the repetitive structure of polarized light separation film and reflective film to give the entire device a thin structure. This is because, were the size of the repetitive structure to be reduced, even smaller triangular prisms would need to be manufactured, and the edges of the prisms would be lost due to polishing so no light will pass through them, resulting in the problem of decreased brightness. In addition, achieving uniform heights among the prisms becomes more difficult the smaller the prism becomes. In addition, problems at the time of pasting the prisms together include angular misalignment, unevenness and bumpiness in the surfaces of light entry and exit, and other problems. Therefore, the edge areas that stick out due to unevenness are susceptible to cracking, and it is difficult to attach other optical elements to the surfaces of light entry and exit. In addition in the event of angular misalignment at the time that the prisms are pasted together, problems occur in which the optic axes of the incident light and emitted light change. The present invention gives proposed solutions to these problems.
In order to solve at least part of the above problems, a first method of the present invention is a method of manufacturing a polarized light separation device that separates light having random directions of polarization into two types of polarized light, comprising the steps of: forming a substrate block having a repetitive structure of a first substrate plate, a polarized light separation layer, a second substrate plate and a reflective layer; and cutting the substrate block at a predetermined angle with respect to surfaces of the substrate plates.
The above method has the meritorious effect that there is no need to polish the surfaces for the individual polarized light separation layers and reflective layers. In addition, it has the meritorious effect that the degree of parallelism between the repeated polarized light separation layers and reflective layers is higher than that of a structure wherein individual tetrahedral prisms are pasted together. Moreover, polarized light separation devices of the same structure with the same characteristics can be manufactured easily in large numbers by cutting them out of the substrate block.
In the first method, the step of forming a substrate block preferably comprises the steps of: forming the polarized light separation layers upon the first substrate plates; forming the reflective layers upon the second substrate plates; and alternately stacking the first substrate plates upon which the polarized light separation layers are formed and the second substrate plates upon which the reflective layers are formed. In this manner, the substrate block can be formed easily.
Further in the first method, in the step of alternately stacking the first substrate plates upon which the polarized light separation layers are formed and the second substrate plates upon which the reflective layers are formed, it is preferable that the first substrate plates and the second substrate plates are stacked alternately with their ends slightly offset by an amount depending on an angle at which the substrate block is to be cut.
By stacking the substrates with their ends slightly offset, the amount of substrate waste generated at the time of cutting of the substrate blocks can be reduced.
In the first method, the step of forming a substrate block preferably comprises the steps of: forming the polarized light separation layers upon the first substrate plates; forming the reflective layers upon the second substrate plates; stacking together one of the first substrate plates upon which the polarized light separation layers are formed and one of the second substrate plates upon which the reflective layers are formed, to thereby form a basic block; and stacking together a plurality of the basic blocks. In this manner, by merely stacking multiple substrate blocks, substrate blocks of the desired size can be formed easily.
In the step of stacking together a plurality of the basic blocks, the basic blocks are preferably stacked with their ends slightly offset by an amount depending on an angle at which the substrate block is to be cut. In this manner, the amount of substrate waste generated at the time of cutting of the substrates can be reduced.
Preferably the first method further comprises the step of: polishing a cut surface after the step of cutting the substrate block at a predetermined angle. The two cut surfaces polished in this manner will become flat surfaces of light entry and exit.
Preferably the first method further comprises the step of: stacking a dummy substrate upon at least one of the substrates making up both surfaces of the substrate block after the substrate block is formed. In this manner, the periphery is not damaged by cracking or breakage, and the loss of light passing through the periphery can be reduced.
Preferably, in the first method, the first substrate plate and the second substrate plate are polished glass plates. The polished glass plate is preferably white glass plates or non-alkali glass. Alternately, the first substrate plate and the second substrate plate are preferably float glass. By using polished plate glass or float glass, the precision of repetition of the polarized light separation film and reflective film can be easily improved inexpensively.
In the first method, one of the first substrate plate and the second substrate plate is preferably a colored light-transparent substrate and the other is a colorless light-transparent substrate. In this manner, the positions of the polarized light separation layers and reflective layers can be easily distinguished.
The reflective film may be made of a thin aluminum film or a thin dielectric film. Alternatively, the reflective film may be made of a thin aluminum film and a thin dielectric film.
A first polarized light separation device according to the present invention is manufactured by any one of the above methods of manufacturing a polarized light separation device. By means of this polarized light separation device, the repetitive structure of polarized light separation layers and reflective layers can be set depending on the thickness and quantity of substrates. In other words, by fine repetition, a large number of repetitive structures can be comprised within a thin substrate. The degree of parallelism between the repeated polarized light separation layers and reflective layers is determined by the precision of the substrate, so a high degree of parallelism can be obtained easily. In addition, the arrangement of repetition can also be configured regularly with high precision. In addition, the surfaces of light entry and exit are clean so phase plates may be attached, anti-reflection films can be applied and other processing can be performed easily.
The first polarized light conversion device preferably comprises: polarized light conversion means, provided on a light exit surface side of the polarized light separation device, for converting light having two types of polarized light components separated from the polarized light separation layer into light having one type of polarized light component. In this manner, light having two types of polarized light components can be provided as incident light and light having one type of polarized light components can be obtained as emitted light.
The polarized light conversion means is preferably a xcex/2 phase layer provided against one of a light exit surface of the first substrate and a light exit surface of the second substrate. In this manner, one type of linearly polarized light can be obtained as emitted light.
In the polarized light conversion device, an anti-reflection film is preferably provided on at least one of a light entry surface side and a light exit surface side. In this manner, the loss of light due to reflection at the surface can be reduced.
A first projection display apparatus according to the present invention comprises: a light source, an integrator optical system having a first lens plate and second lens plate that divide light from the light source into a plurality of light fluxes; any one of the above mentioned polarized light conversion devices; modulation means for modulating light emitted by the polarized light conversion device; and a projection optical system that projects the light modulated by the modulation means.
A second projection display apparatus according to the present invention comprises: a light source; an integrator optical system having a first lens plate and a second lens plate that divide light from the light source into a plurality of light fluxes; any one of the above mentioned polarized light conversion devices; a color-separating optical system that separates light emitted from the polarized light conversion device into light of a plurality of colors; modulation means for individually modulating the plurality of colors of light separated by the color-separating optical system; a synthesizing optical system that synthesizes the light modulated by the modulation means; and a projection optical system that projects the light synthesized by the synthesizing optical system.
It is preferably that transmittance characteristic of the polarized light separation film is adjusted so that differences in transmittance with respect to light of a wavelength corresponding to peaks at various colors are at most about 5% when the light of a wavelength corresponding to the peaks at various colors in the spectrum of the light that enters the polarized light separation film enters at a difference in an angle of incidence within a predetermined range.
A second polarized light separation device according to the present invention comprises: a substrate block having a light entry surface, a light exit surface substantially parallel to the light entry surface, and a plurality of light-transparent substrates, which are pasted together sequentially at a plurality of interfaces that assume a predetermined angle with respect to the light entry surface and the light exit surface, the substrate block further having a plurality of polarized light separation films and a plurality of reflective films provided alternately on the plurality of interfaces; and a position-identifying part provided on at least one of two side surfaces of the substrate block formed roughly perpendicularly to the plurality of interfaces, the position-identifying part being usable at the time of positioning of the polarized light separation device.
By means of the second polarized light separation device, a position-identifying part is provided on the side surface of the polarized light separation device, so when the polarized light separation device is used in another apparatus, it can be positioned relatively accurately.
In the second polarized light separation device, the position-identifying part is preferably located at a position which is roughly equidistant from two other side surfaces adjacent to the side surfaces upon which the position-identifying part is provided. In this manner, the positioning precision at the center of the optical element can be increased.
Alternatively, the position-identifying part is preferably located at a position which has different distances from the two other side surfaces adjacent to both of the side surfaces upon which the position-identifying part is provided. In this manner, the orientation of the polarized light separation device can be determined from the position-identifying part.
The position-identifying part may be a projection provided on the side surface; or the position-identifying part may be an indentation provided on the side surface. Alternatively, the position-identifying part may be a portion marked with a particular color different than that of the rest of the side surface.
A second method of manufacturing a polarized light separation device according to the present invention comprises the steps of: (a) alternately pasting together a plurality of light-transparent substrates at a plurality of interfaces to form a compound plate member that has a plurality of polarized light separation films and a plurality of reflective films provided alternately on the plurality of interfaces; (b) cutting the compound plate member at a predetermined angle with respect to the plurality of interfaces to generate a substrate block that has substantially parallel light entry and light exit surfaces; and (c) polishing the light entry surface and the light exit surface of the substrate block; wherein the step (a) comprises the step of forming an position-identifying part, that is usable at the time of positioning of the polarized light separation device, on at least one of side surfaces of the substrate block formed roughly perpendicular to the plurality of interfaces. Thus the aforementioned second polarized light separation device can be manufactured by means of the second method.
The second method preferably comprises the step of: (d) polishing the light entry surface and the light exit surface of the substrate block. In this manner, surfaces of light entry and exit of the substrate block forming the polarized light separation device can be polished easily, so the polarized light separation device can be manufactured easily.
In the second method, the step (a) preferably includes the step of: forming a projection as the position-identifying part by offsetting at least some of the plurality of light-transparent substrates from the other light-transparent substrates. In this manner, the projection used as the position-identifying part can be formed precisely and easily.
A polarized light conversion device according to the present invention comprises: a polarized light separation device according to any one of the above second method for a polarized light separation device; and polarized light conversion means, provided on a light exit surface side of the polarized light separation device, for converting light having two types of polarized light components separated from the polarized light separation layer into light having one type of polarized light component.
The polarized light conversion means preferably is a xcex/2 phase layer provided against the light exit surface of every other substrate among the light exit surfaces of the substrates. Further, an anti-reflection film is preferably provided on at least one of the light entry surface side and the light exit surface side.
A third projection display apparatus according to the present invention comprises: a light source; an integrator optical system having a first lens plate and a second lens plate that divide the light from the light source into a plurality of light fluxes; a polarized light conversion device according to any one of the seventh invention; modulation means for modulating light emitted by the polarized light conversion device; and a projection optical system that projects the light modulated by the modulation means.
A fourth projection display apparatus according to the present invention comprises: a light source; an integrator optical system having a first lens plate and a second lens plate :that divide the light from the light source into a plurality of light fluxes; a polarized light conversion device according to any one of the seventh invention; a color-separating optical system that separates light emitted from the polarized light conversion device into light of a plurality of colors; modulation means for individually modulating the plurality of colors of light separated by the color-separating optical system; a synthesizing optical system that synthesizes the light modulated by the modulation means; and a projection optical system that projects the light synthesized by the synthesizing optical system.